OKLAHOMA CITY — Supporters of Richard Glossip threw a Hail Mary pass Monday, in an attempt to spare him from his September execution date.

The Oklahoma Coalition to Abolish the Death Penalty held a press conference where a group of dignitaries, attorneys and religious authorities pleaded multiple arguments for why they believe the convicted murderer’s life should be spared: Some argued he is innocent, others said his sentence outweighed his crimes.

Sister Helen Prejean, the nun and anti-death penalty activist known for the book and movie “Dead Man Walking,” appeared on Glossip’s behalf, saying he’s “the sweetest person I have ever met. He has found a way to live in peace where he is.”

Glossip was convicted in 1997 of first-degree murder for the beating of Barry Alan Van Treese at the Best Budget Inn in Oklahoma City. Glossip has maintained his innocence for more than 17 years, denying prosecutors’ assertions that he plotted the murder that Justin Sneed carried out when he beat Van Treese with a baseball bat.

Glossip was also the lead plaintiff in a lawsuit that went all the way to the U.S. Supreme Court, with a group of Oklahoma inmates challenging the state’s use of the sedative midazolam in executions. Their lawsuit argued the drug could cause pain or suffering and violate the Eighth Amendment. The drug was first used by Oklahoma in the botched 2014 execution of Clayton Lockett.

On June 29, the Supreme Court upheld Oklahoma’s three-drug lethal injection protocol using midazolam. After this decision, Oklahoma’s Attorney General Scott Pruitt requested that Glossip’s execution date be set for Sept. 16.

At Monday’s press conference, attorney Donald Knight and Prejean advocated for Glossip’s innocence and made it clear that they would be doing everything in their power to continue forms of investigation.

“As I looked into the case, chills rolled down my spine,” Knight said.

Knight made a plea for Glossip’s innocence and claimed that the criminal case was “deeply flawed” and one of the “weakest” death penalty cases he has seen. He said he plans to continue to investigate Glossip’s case.

Knight reminded the media that Glossip was not convicted of committing any crimes prior to landing on death row. The death penalty should only be reserved for “the worst of the worst” cases, he said. Glossip is not in this category, he said.

Knight insinuated that there were other “unsavory” people staying at the Best Budget Inn who could have been involved in Van Treese’s killing. Glossip’s conviction is the results of mistakes and flaws or our capital punishment system, he said.

The Rev. Adam Leathers, a spokesman for the coalition, was scheduled to speak Monday, but former Oklahoma Sen. Connie Johnson, a chairwoman for the group, said Leathers couldn’t attend because he is healing from a bat bite.

Prejean said that Glossip is not the “worst of the worst,” but simply “innocent.”

Prejean is famously the author of “Dead Man Walking: An Eyewitness Account of the Death Penalty in the United States.” Her work was nominated for a Pulitzer Prize and later transformed into an Oscar-nominated film.

Prejean began working with Glossip after he wrote her a letter declaring his innocence. She said she is doing everything in her power to fight for Glossip’s life.

“We are fighting like ‘you know what’ behind the scenes, and I know the uphill battle we have but you got to fight,” she said. “You have to do everything you can. You have to get lawyers, you have to get investigators, you got to make an appeal to people, come forward.”

Without new evidence, the legal system has run its course and Glossip will face the death penalty. He was denied clemency in 2014 by the Oklahoma Pardon and Parole Board.

Because of the Supreme Court ruling, a judge in Oklahoma’s Western District of federal court could potentially enter a stay allowing Glossip to have a full trial on the state’s use of midazolam.

But Oklahoma officials have said Glossip has already had far beyond his day in court and they intend to follow through on his execution.